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Error code: VTGC(2)

Error: An error occurred in the renaming clause of a formal generic.
What to do:
  In the case of a multi-constraint generic (like in  'G -> {A,B}')
  one has to ensure that for every used feature there are no ambiguities.
  In order to achieve that goal you can use a renaming clause.
  For example: G -> {A rename f as g end, B}
Hint: The renaming for formal generics is analogous to the
  renaming occurring during inheritance.

Class: BB [G -> CC rename f as g, f as g end]
Renaming of constraint class: CC
  at position #1  of formal G
The following features have been renamed multiple times:
   `f' (is renamed to `g', `g')

The following features have been renamed and produce one or more conflicts:
   `g' is in conflict because:
      more than one feature is renamed to it: `f', `f'

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